- ID:
- ivo://CDS.VizieR/J/ApJ/829/23
- Title:
- Stellar flares from Q0-Q17 Kepler LCs
- Short Name:
- J/ApJ/829/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A homogeneous search for stellar flares has been performed using every available Kepler light curve. An iterative light curve de-trending approach was used to filter out both astrophysical and systematic variability to detect flares. The flare recovery completeness has also been computed throughout each light curve using artificial flare injection tests, and the tools for this work have been made publicly available. The final sample contains 851168 candidate flare events recovered above the 68% completeness threshold, which were detected from 4041 stars, or 1.9% of the stars in the Kepler database. The average flare energy detected is ~10^35^erg. The net fraction of flare stars increases with g-i color, or decreasing stellar mass. For stars in this sample with previously measured rotation periods, the total relative flare luminosity is compared to the Rossby number. A tentative detection of flare activity saturation for low-mass stars with rapid rotation below a Rossby number of ~0.03 is found. A power-law decay in flare activity with Rossby number is found with a slope of -1, shallower than typical measurements for X-ray activity decay with Rossby number.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/657/A41
- Title:
- Stellar halo of NGC 5128 (Centaurus A)
- Short Name:
- J/A+A/657/A41
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The extended stellar halos of galaxies contain important clues for investigating their assembly history and evolution. We investigate the resolved stellar content and the extended halo of NGC 5128 as a function of galactocentric distance, and trace the halo outward to its currently detectable limits. We used Hubble Space Telescope images obtained with the WFPC2, ACS, and WFC3 cameras equipped with F606W and F814W filters to resolve individual red giant branch (RGB) stars in 28 independent pointings across the halo of NGC 5128. The stellar halo analysis for 14 of these pointings is presented here for the first time. Star counts from deep VI color-magnitude diagrams reaching at least 1.5mag below the tip of the RGB are used to derive the surface density distribution of the halo. The contamination by Milky Way stars is assessed with a new control field, with models, and by combining optical and near-IR photometry. We present a new calibration of the WFC3 F606W + F814W photometry to the ground-based VI photometric system. The photometry shows that the stellar halo of NGC 5128 is dominated by old RGB stars that are present in all fields. The V-band surface brightness of fields changes from 23 to 32mag/arcsec^2^ between the innermost field only 8.3kpc from the galaxy center to our outermost halo fields, which are located 140 kpc away from the center along the major axis and 92 kpc along the minor axis. Within the inner ~30kpc, we also find evidence for a 2-3Gyr old population traced by asymptotic giant branch stars that are brighter than the tip of the RGB. This population contributes only up to 10% in total stellar mass if it is 2Gyr old, but a larger fraction of 30-40% is required if its age is 3Gyr. The stellar surface density profile is well fit by a classic r^1/4^ curve or a simple power-law form ~r^-3.1^ over the full radial range, with no obvious break in the slope, but with large field-to-field scatter. The ellipticity measured from integrated-light photometry in the inner parts, e=(b/a)=0.77, flattens to e=0.54+/-0.02 beyond 30kpc. Considering the flattening of the outer halo, the projection of the elliptical isophote on the semimajor axis for our most distant field reaches nearly 30 effective radii.
- ID:
- ivo://CDS.VizieR/J/ApJ/786/L10
- Title:
- Stellar IMF mass normalization for z~1 galaxies
- Short Name:
- J/ApJ/786/L10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The stellar initial mass function (IMF) is a key parameter for studying galaxy evolution. Here we measure the IMF mass normalization for a sample of 68 field galaxies in the redshift range 0.7-0.9 within the Extended Groth Strip. To do this we derive the total (stellar + dark matter) mass-to-light [(M/L)] ratio using axisymmetric dynamical models. Within the region where we have kinematics (about one half-light radius), the models assume (1) that mass follows light, implying negligible differences between the slope of the stellar and total density profiles, (2) constant velocity anisotropy ({beta}_z_=1-{sigma}_z_^2^/{sigma}_R_^2^=0.2), and (3) that galaxies are seen at the average inclination for random orientations (i.e., i=60{deg}, where i=90{deg} represents edge-on). The dynamical models are based on anisotropic Jeans equations, constrained by Hubble Space Telescope/Advanced Camera for Surveys imaging and the central velocity dispersion of the galaxies, extracted from good-quality spectra taken by the DEEP2 survey. The population (M/L) are derived from full-spectrum fitting of the same spectra with a grid of simple stellar population models. Recent dynamical modeling results from the ATLAS^3D^ project and numerical simulations of galaxy evolution indicate that the dark matter fraction within the central regions of our galaxies should be small. This suggests that our derived total (M/L) should closely approximate the stellar M/L. Our comparison of the dynamical (M/L) and the population (M/L) then implies that for galaxies with stellar mass M_*_>~10^11^ M_{sun}_, the average normalization of the IMF is consistent with a Salpeter slope, with a substantial scatter. This is similar to what is found within a similar mass range for nearby galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/596/437
- Title:
- Stellar-mass black holes in the SDSS
- Short Name:
- J/ApJ/596/437
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We search for nearby, isolated, accreting, "stellar-mass" (3-100M_{sun}_) black holes. Models suggest a synchrotron spectrum in visible wavelengths and some emission in X-ray wavelengths. Of 3.7 million objects in the Sloan Digital Sky Survey Early Data Release, Cat. <J/AJ/123/567>, about 150,000 objects have colors and properties consistent with such a spectrum, and 87 of these objects are X-ray sources from the ROSAT All-Sky Survey (Cat. <IX/10> and <IX/29>). Thirty-two of these have been confirmed not to be black holes using optical spectra. We give the positions and colors of these 55 black hole candidates and quantitatively rank them on their likelihood to be black holes. We discuss uncertainties in the expected number of sources and the contribution of black holes to local dark matter.
- ID:
- ivo://CDS.VizieR/J/MNRAS/401/1521
- Title:
- Stellar masses of Lyman break galaxies at z~3
- Short Name:
- J/MNRAS/401/1521
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a large survey of the mid-infrared (mid-IR) properties of 248 Lyman Break Galaxies (LBGs) with confirmed spectroscopic redshift using deep Spitzer/Infrared Array Camera (IRAC) observations in six cosmological fields. By combining the new mid-IR photometry with optical and near-infrared observations, we model the spectral energy distributions (SEDs) employing a revised version of the Bruzual and Charlot synthesis population code that incorporates a new treatment of the thermal-pulsating asymptotic giant branch phase (CB07). Our primary aim is to investigate the impact of the AGB phase in the stellar masses of the LBGs, and compare our new results with previous stellar mass estimates. We investigate the stellar mass of the LBG population as a whole and assess the benefits of adding longer wavelengths to estimates of stellar masses for high-redshift galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/675/234
- Title:
- Stellar mass functions for galaxies 0<z<4
- Short Name:
- J/ApJ/675/234
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using a sample of ~28000 sources selected at 3.6-4.5um with Spitzer observations of the Hubble Deep Field North, the Chandra Deep Field South, and the Lockman Hole (surveyed area ~664arcmin^2^), we study the evolution of the stellar mass content of the universe at 0<z<4. We calculate stellar masses and photometric redshifts, based on ~2000 templates built with stellar population and dust emission models fitting the ultraviolet to mid-infrared spectral energy distributions of galaxies with spectroscopic redshifts. We estimate stellar mass functions for different redshift intervals.
- ID:
- ivo://CDS.VizieR/J/MNRAS/506/928
- Title:
- Stellar mass-size relation for low M* galaxies
- Short Name:
- J/MNRAS/506/928
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We reliably extend the stellar mass-size relation over 0.2<=z<=2 to low stellar mass galaxies by combining the depth of Hubble Frontier Fields (HFF) with the large volume covered by CANDELS. Galaxies are simultaneously modelled in multiple bands using the tools developed by the MegaMorph project, allowing robust size (i.e., half-light radius) estimates even for small, faint, and high redshift galaxies. We show that above 10^7^M_{sun}_, star-forming galaxies are well represented by a single power law on the mass-size plane over our entire redshift range. Conversely, the stellar mass - size relation is steep for quiescent galaxies with stellar masses >=10^10.3^M_{sun}_ and flattens at lower masses, regardless of whether quiescence is selected based on star-formation activity, rest-frame colours, or structural characteristics. This flattening occurs at sizes of ~1kpc at z<=1. As a result, a double power law is preferred for the stellar mass-size relation of quiescent galaxies, at least above 10^7^M_{sun}_. We find no strong redshift dependence in the slope of the relation of star-forming galaxies as well as of high mass quiescent galaxies. We also show that star-forming galaxies with stellar masses >=10^9.5^M_{sun}_ and quiescent galaxies with stellar masses>=10^10.3^M_{sun}_ have undergone significant size growth since z~2, as expected; however, low mass galaxies have not. Finally, we supplement our data with predominantly quiescent dwarf galaxies from the core of the Fornax cluster, showing that the stellar mass-size relation is continuous below 10^7^M_{sun}_, but a more complicated functional form is necessary to describe the relation.
- ID:
- ivo://CDS.VizieR/J/AJ/157/216
- Title:
- Stellar multiplicity rate of M dwarfs within 25 pc
- Short Name:
- J/AJ/157/216
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of the largest, most comprehensive study ever done of the stellar multiplicity of the most common stars in the Galaxy, the red dwarfs. We have conducted an all-sky volume-limited survey for stellar companions to 1120 M dwarf primaries known to lie within 25 pc of the Sun via trigonometric parallaxes. In addition to a comprehensive literature search, stars were explored in new surveys for companions at separations of 2"-300". A reconnaissance of wide companions to separations of 300" was done via blinking archival images. I-band images were used to search our sample for companions at separations of 2"-180". Various astrometric and photometric methods were used to probe the inner 2" to reveal close companions. We report the discovery of 20 new companions and identify 56 candidate multiple systems. We find a stellar multiplicity rate of 26.8+/-1.4% and a stellar companion rate of 32.4+/-1.4% for M dwarfs. There is a broad peak in the separation distribution of the companions at 4-20 au, with a weak trend of smaller projected linear separations for lower mass primaries. A hint that M-dwarf multiplicity may be a function of tangential velocity is found, with faster moving, presumably older, stars found to be multiple somewhat less often. We calculate that stellar companions make up at least 17% of mass attributed to M dwarfs in the solar neighborhood, with roughly 11% of M-dwarf mass hidden as unresolved companions. Finally, when considering all M-dwarf primaries and companions, we find that the mass distribution for M dwarfs increases to the end of the stellar main sequence.
- ID:
- ivo://CDS.VizieR/J/A+A/425/927
- Title:
- Stellar objects in the Serpens cloud field
- Short Name:
- J/A+A/425/927
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present near infrared (J, H and Ks) observations of a 5'x10' sample field in the Serpens Star Formation region obtained with SOFI at the NTT. These observations are sensitive enough to detect a 20M_Jup_ brown dwarf through an extinction of A_V_~16 and are used to build an infrared census of this field in the cluster. From photometry and mass-luminosity models, we have developed a detailed methodology to extract quantitative parameters (distance modulus, extinction, spectral type, masses) for objects observed towards and inside the Serpens molecular cloud. An extinction map of the region is derived allowing us to disentangle cloud members from background field objects. Luminosities and masses for 14 low-mass stars and substellar object candidate members of the cluster are derived.
- ID:
- ivo://CDS.VizieR/J/AJ/159/230
- Title:
- Stellar occultation by (541132) Leleakuhonua
- Short Name:
- J/AJ/159/230
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A stellar occultation by the extreme large-perihelion trans-Neptunian object (541132)-Leleakuhonua (also known by the provisional designation of 2015TG_387_) was predicted by the Lucky Star project and observed with the Research and Education Collaborative Occultation Network (RECON) on 2018-October-20-UT. A single detection and a nearby nondetection provide constraints for the size and albedo. When a circular profile is assumed, the radius is r=110_-10_^+14^km, corresponding to a geometric albedo p_V_=0.21_-0.05_^+0.03^, for an adopted absolute magnitude of HV=5.6, typical of other objects in dynamically similar orbits. The occultation also provides a high-precision astrometric constraint.
